Symbol or emoji?
Unicode added the twelve zodiac characters in version 1.1, in 1993, long before emoji. It now marks them to be shown as emoji by default, so most phones draw them as colored emoji. The invisible variation selector U+FE0E after a sign asks for the symbol, and U+FE0F asks for the emoji. The choice at the top of the page sets which one the copy buttons add. The other symbols here have no emoji form and copy as they are.
Where the symbols come from
The sign symbols are small pictures: the ram's horns of Aries, the bull's head of Taurus, the centaur's arrow of Sagittarius, the goat with a fish's tail of Capricorn and the ripples of water of Aquarius. A few are less certain. Virgo's is often said to come from ΠΑΡ, short for the Greek parthenos, "maiden", and Cancer's and Leo's are usually read as a crab's claws and a lion's head and tail.
The classical planets' symbols are mostly abbreviations or attributes of their gods. Jupiter's is a Greek Ζ for Zeus and Saturn's the letters κρ for Cronus, each with a bar that marked an abbreviation. Mars has his shield and spear, Venus her hand mirror and Mercury his caduceus, which gained its cross-bar after the 11th century.
The newer bodies got newer symbols. Uranus's orb carries an H for William Herschel, who found the planet in 1781; astronomers use a different sign, ⛢. Neptune has his trident, and Pluto either the letters PL, for Pluto and Percival Lowell, or an orb above a bident. Chiron's key also spells OK, for Object Kowal, its name when it was announced. Unicode added Chiron, Black Moon Lilith, the four asteroids, the sextile and three minor aspects in version 5.1 in 2008, and the Part of Fortune only in version 15.0 in 2022.
The aspect symbols are geometry: a triangle for the trine, a square for the square, the lines of a hexagon for the sextile and its halves for the semisextile and quincunx.
Symbols in a chart
A birth chart wheel uses all of these at once: the sign symbols around the rim, the planet symbols inside at their degrees, ℞ beside any planet that was retrograde, and colored aspect lines across the middle. The aspects guide explains what each angle means, and the zodiac sign calculator finds your sign from your birthday.
Sources
Characters, names and versions: the Unicode Character Database, version 18.0. What each shape shows: Wikipedia's "Astrological symbols" (revision of April 27, 2026), which marks some of the older readings as uncertain; this page says "usually read as" or "often said" for those.